The aim of this research is to investigate the effect of an atypical child on family patterns and processes. The basic hypothesis underlying this project is that parental practices are directly related to parental belief systems about child development in general and to one's own children's competence and adjustment in particular. These beliefs are constructed by the parent and are in part dependent on information obtained from interactions with each child in the family, i.e., from both the children in the family that do and that do not deviate from the norm. Therefore, the relationship of family size and the ordinal position of the atypical child to parental beliefs and to each child's cognitive and social-personality development will be investigated within the context of the research design. Specifically, the study addresses four problems within the context of a design comparing families with and without an atypical child: (1) the effect of the atypical child's level of functioning and position in the family constellation on parental beliefs and marital adjustment; (2) the relationship between parental beliefs about normal child development and with respect to their own child who may deviate from the norm or parental expectations; (3) the relationship between these perspectives and actual parental behaviors when interacting with the child; and (4) the nature of sibling-sibling interactions given different ordinal positions of the atypical child across the families included in the study. Data will be gathered with the use of in-depth interviews, self-rating scales, observations of parent-child and sibling interaction; and standard intellectual assessments.